Fix flaky test_collection_metadata

[crusaderky]

Fix occasional test failure

__________________________ test_collections_metadata ___________________________

c = <Client: No scheduler connected>
s = <Scheduler 'tcp://127.0.0.1:50135', workers: 0, cores: 0, tasks: 0>
a = <Worker 'tcp://127.0.0.1:50136', name: 0, status: closed, stored: 0, running: 0/1, ready: 0, comm: 0, waiting: 0>
b = <Worker 'tcp://127.0.0.1:50139', name: 1, status: closed, stored: 0, running: 0/2, ready: 0, comm: 0, waiting: 0>

    @pytest.mark.filterwarnings("ignore:Dask annotations")
    @gen_cluster(client=True)
    async def test_collections_metadata(c, s, a, b):
        np = pytest.importorskip("numpy")
        pd = pytest.importorskip("pandas")
        dd = pytest.importorskip("dask.dataframe")
        df = pd.DataFrame(
            {"x": np.random.random(1000), "y": np.random.random(1000)},
            index=np.arange(1000),
        )
        ldf = dd.from_pandas(df, npartitions=10)
    
        with span("foo") as span_id:
            await c.compute(ldf)
    
        ext = s.extensions["spans"]
        span_ = ext.spans[span_id]
        assert span_
>       collections_meta = span_.metadata["collections"]
                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
E       TypeError: 'NoneType' object is not subscriptable

distributed/tests/test_spans.py:840: TypeError

WIP unreviewed clanker output; please disregard for now

[github-actions]

Unit Test Results

See test report for an extended history of previous test failures. This is useful for diagnosing flaky tests.

    19 files   -     21      19 suites   - 21   16h 34m 20s ⏱️ + 1h 33m 58s
 5 000 tests +   846   5 000 ✅ +1 025       0 💤  -   178  0 ❌  - 1 
95 000 runs  +14 159  85 000 ✅ +8 397  10 000 💤 +5 763  0 ❌  - 1 

Results for commit 6fa439b. ± Comparison against base commit ace5560.

This pull request removes 4154 and adds 5000 tests. Note that renamed tests count towards both.

distributed.cli.tests.test_dask_scheduler ‑ test_dashboard
distributed.cli.tests.test_dask_scheduler ‑ test_dashboard_allowlist
distributed.cli.tests.test_dask_scheduler ‑ test_dashboard_non_standard_ports
distributed.cli.tests.test_dask_scheduler ‑ test_dashboard_port_zero
distributed.cli.tests.test_dask_scheduler ‑ test_defaults
distributed.cli.tests.test_dask_scheduler ‑ test_hostport
distributed.cli.tests.test_dask_scheduler ‑ test_idle_timeout
distributed.cli.tests.test_dask_scheduler ‑ test_interface
distributed.cli.tests.test_dask_scheduler ‑ test_multiple_protocols
distributed.cli.tests.test_dask_scheduler ‑ test_multiple_workers
…

distributed.tests.test_spans ‑ test_collections_metadata[1-5000]
distributed.tests.test_spans ‑ test_collections_metadata[10-5000]
distributed.tests.test_spans ‑ test_collections_metadata[100-5000]
distributed.tests.test_spans ‑ test_collections_metadata[1000-5000]
distributed.tests.test_spans ‑ test_collections_metadata[1001-5000]
distributed.tests.test_spans ‑ test_collections_metadata[1002-5000]
distributed.tests.test_spans ‑ test_collections_metadata[1003-5000]
distributed.tests.test_spans ‑ test_collections_metadata[1004-5000]
distributed.tests.test_spans ‑ test_collections_metadata[1005-5000]
distributed.tests.test_spans ‑ test_collections_metadata[1006-5000]
…

♻️ This comment has been updated with latest results.